The present invention relates generally to communication equipment and in particular the present invention relates to fault notification circuitry.
Communication equipment such as voice or data communication equipment includes hardware components. These hardware components are susceptible to faults and interruptions in operation. For example, cards (circuit boards) used to process or route signals may suffer a complete power interrupt and cease operation. The interruption can result in a system-wide failure that must be corrected. Troubleshooting the system failure can be greatly assisted if the hardware provides an indication of the failure. Numerous cards are often mounted in a rack and are coupled to communication lines. The cards are typically coupled to a processor card (management processor) managing this and other cards for quality of operation. If there is an interruption with a line, a technician needs to be able to determine if there is a problem with the card or a remote problem with the line. Both the technician and the management processor need to be notified of card faults. As such, visual and electronic indicators are often provided.
One method of providing an indication of circuit board failure uses a relay to trigger a warning circuit. The relay can be either mechanical or optical. The warning circuitry can provide a visual indication of failure by illuminating, for instance, one or more light-emitting diodes (LED). The warning circuitry can also provide an error signal that notifies the system processor of the card failure.
Problems with these system-troubleshooting circuits include relatively high cost and power consumption. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for new circuitry to indicate circuit faults and failures.
The above-mentioned problems with fault warning circuitry and other problems are addressed by the present invention and will be understood by reading and studying the following specification.
In one embodiment, a fault indication circuit comprises a light emitting diode (LED), a first transistor coupled in series with the LED to control current flow through the LED, and a second transistor electrically coupled to the first transistor to selectively activate the first transistor in response to a signal provided by an external circuit board. The second transistor maintains the first transistor in a deactivated state while the circuit board is operational.
In another embodiment, a circuit board fault indicator comprises a LED having an anode coupled to an upper supply voltage node via a first resistor, a first transistor coupled between a cathode of the LED and a lower supply voltage node, and a second transistor electrically coupled to a control node of the first transistor to selectively activate the first transistor in response to a signal provided by an external circuit board. A third transistor is coupled between the cathode of the LED and the lower supply voltage node. A control node of the third transistor is coupled to receive a non-fatal fault signal provided by the external circuit board. A fourth transistor is coupled between a signal output node and the lower supply voltage node. In one embodiment a second LED is coupled to be illuminated when the first transistor is inactive.
A method of indicating faults in a communication system monitors an operational status of a circuit and activates a first light emitting diode (LED) if the operational status of the circuit is non-functional.
A method of indicating faults in a communication system monitors an operational status of a circuit and deactivates a second LED if the operational status of the circuit is non-functional. The first LED is activated while the second LED remains active if the operational status of the circuit is a minor fault.